AMD has recently released Catalyst 12.9 driver which adds support to Ubuntu 12.10 (Quantal Quetzal) and Linux 3.5 kernel series. The driver is based on the fglrx 9.00 release and brings more changes, bug fixes, and improvements. The release notes for AMD Catalyst Driver 12.9 is not available currently, but you can get some information about this latest release here.
We will see here two types of driver installation (automatic & manual), but let's first uninstall the current AMD driver with these commands: